The present invention relates to an apparatus for observing a target object by using scattered light and, more particularly, to an apparatus to which a TDI (Time Delay Integration) method by a CCD sensor is applied.
Conventionally, when scattered light from a two-dimensionally moving object or fluid is focused and formed into an image, and the two-dimensional image is converted into an image signal and observed, the image data must be processed by an image processing unit or the like and analyzed because the obtained signal strength is low. Therefore, the observation apparatus becomes bulky, and a long time is required for observation.
In addition, since scattering due to a defect in a semiconductor wafer, or dust or a defect on a wafer is generally very weak, a bulky apparatus and a long observation time are necessary.
It is an object of the present invention to provide an observation apparatus having a simple arrangement, which can observe a defect of a moving target object or semiconductor wafer by using scattered light in real time with a high sensitivity in accordance with the movement of the target object.
In order to achieve the above object, according to the present invention, there is provided an observation apparatus comprising a CCD sensor which: has, on a light-receiving surface, pixel lines each including a plurality of pixels, sequentially shifts the charge signals of the pixels of each line, each of which is generated and integrated upon receiving light, to the adjacent line, and sequentially outputs the charge signals through the line at one end; illuminating means for illuminating a moving observation target with a laser beam; imaging means for focusing scattered light from the moving observation target to form an image on the light-receiving surface; and driving means for driving the CCD such that the shift speed of the charge signals matches a moving speed of the image on the light-receiving means.
The CCD sensor and the driving means may have a function of shifting the charge signals in the direction perpendicular to the shift direction. In addition, the CCD sensor preferably has a shift register for receiving the charge signals of the pixels of the line at one end, shifting the received charge signals to sequentially output each charge signal, and a dark current buffer for storing charge signals of a dark current output to the shift register through the line at one end, and outputs contents obtained by subtracting, from contents of the shift register, corresponding contents of the dark current buffer.